Aftertreatment system for motor vehicle

ABSTRACT

An aftertreatment system for an internal combustion engine includes a diesel cold start catalyst member, a lean NOx trap (LNT) member arranged directly adjacent to and downstream of the diesel cold start catalyst, and a selective catalyst reduction (SCR) member arranged downstream of the LNT. The diesel cold start catalyst is operable to reduce NOx emissions at operating temperatures below 200° C. and the LNT and SCR system are operable to reduce NOx emissions at operating temperatures above 200° C.

INTRODUCTION

The subject disclosure relates to the art of aftertreatment systems and,more particularly, to an aftertreatment system for a motor vehicle.

Internal combustions engines, when operated, often produce undesirablegases such as CO, CO2, NOx, and the like. Many countries have introducedregulations limiting emissions from internal combustion engines. Variousaftertreatment systems have been introduced to reduce emissions. In manyinstances, existing aftertreatment systems operate during normaloperating conditions. During normal operating conditions, exhaustcomponents have been heated to operating temperatures which may be inexcess of about 175° C.

New emissions regulations are being implemented to address emissionsthat may occur below normal operating temperatures. Currentaftertreatment systems may employ an electric heater positioned to heatan aftertreatment catalyst to further reduce emissions during, forexample, cold starts. Electric heaters add additional components thatnecessitate periodic maintenance and increase an overall complexity ofaftertreatment devices. Further, electric heaters require a warm upperiod during such time as emissions may occur at levels that do notmeet current and pending regulations. Accordingly, it is desirable toprovide an aftertreatment system that operates during cold starts toreduce emissions of an internal combustion engine operating below normaloperating temperatures.

SUMMARY

In one exemplary embodiment, an aftertreatment system for an internalcombustion engine includes a diesel cold start catalyst member, a leanNOx trap (LNT) member arranged directly adjacent to and downstream ofthe diesel cold start catalyst, and a selective catalyst reduction (SCR)member arranged downstream of the LNT. The diesel cold start catalyst isoperable to reduce NOx emissions at operating temperatures below 200° C.and the LNT and SCR system are operable to reduce NOx emissions atoperating temperatures above 200° C.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include a diesel exhaustfluid (DEF) injection system operable to introduce a diesel exhaustfluid into exhaust gases produced by the internal combustion engine.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include wherein the DEFinjection system is arranged downstream of the LNT and upstream of theSCR.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include a transfer tubefluidically connecting the diesel cold start catalyst and LNT with theSCR.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include wherein the DEFinjection system is fluidically connected to the transfer tube.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include wherein the DEFinjection system comprises a urea injector.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include at least one of anO2/NOx sensor and an exhaust gas temperature (EGT) sensor arrangedupstream of the diesel cold start catalyst, and at least one of anO2/NOx sensor and an EGT sensor arranged downstream of the LNT.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include a firstdifferential pressure sensor (DPS) arranged upstream of the SCR and asecond DPS arranged downstream of the SCR.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include wherein the dieselcold start catalyst and LNT are arranged in a common housing.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include a rear oxidationcatalyst (ROC) arranged downstream of the SCR.

In accordance with another aspect of an exemplary embodiment, a motorvehicle includes an internal combustion engine including an exhaustsystem, and an aftertreatment system fluidically connected to theexhaust system. The aftertreatment system includes a diesel cold startcatalyst (diesel cold start catalyst) member, a lean NOx trap (LNT)member arranged directly adjacent to and downstream of the diesel coldstart catalyst, and a selective catalyst reduction (SCR) member arrangeddownstream of the LNT. The diesel cold start catalyst is operable toreduce NOx emissions at operating temperatures below 200° C. and the LNTand SCR system are operable to reduce NOx emissions at operatingtemperatures above 200° C.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include a diesel exhaustfluid (DEF) injection system operable to introduce a diesel exhaustfluid into exhaust gases produced by the internal combustion engine.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include wherein the DEFinjection system is arranged downstream of the LNT and upstream of theSCR.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include a transfer tubefluidically connecting the diesel cold start catalyst and LNT with theSCR.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include wherein the DEFinjection system is fluidically connected to the transfer tube.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include wherein the DEFinjection system comprises a urea injector.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include a diesel exhaustfluid (DEF) injection system arranged downstream of the LNT.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include at least one of anO2/NOx sensor and an exhaust gas temperature (EGT) sensor arrangedupstream of the diesel cold start catalyst, and at least one of anO2/NOx sensor and an EGT sensor arranged downstream of the LNT.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include a firstdifferential pressure sensor (DPS) arranged upstream of the SCR and asecond DPS arranged downstream of the SCR.

In addition to one or more of the features described above or below, oras an alternative, further embodiments could include wherein the dieselcold start catalyst and LNT are arranged in a common housing.

The above features and advantages, and other features and advantages ofthe disclosure are readily apparent from the following detaileddescription when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages and details appear, by way of example only,in the following detailed description, the detailed descriptionreferring to the drawings in which:

FIG. 1 depicts a motor vehicle having an exhaust aftertreatment system,in accordance with an aspect of an exemplary embodiment; and

FIG. 2 is a block diagram depicting an exhaust aftertreatment system, inaccordance with an aspect of an exemplary embodiment.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, its application or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

A motor vehicle, in accordance with an aspect of an exemplaryembodiment, is indicated generally at 10 in FIG. 1. Motor vehicle 10 isshown in the form of a pickup truck. It is to be understood that motorvehicle 10 may take on various forms including automobiles, commercialtransports, marine vehicles, and the like. Motor vehicle 10 includes abody 12 having an engine compartment 14, a passenger compartment 15, anda cargo bed 17. Engine compartment 14 houses an internal combustionengine system 24 which, in the exemplary embodiment shown, may include adiesel engine 26. Internal combustion engine system 24 includes anexhaust system 30 that is fluidically connected to an exhaustaftertreatment system 34. Exhaust produced by internal combustion enginesystem 24 passes through aftertreatment system 34 to reduce NOxemissions that may exit to ambient through an exhaust outlet pipe 36.

In accordance with an aspect of an exemplary embodiment illustrated inFIG. 2, internal combustion engine system 24 may include a turbocharger40 having a compressor portion 42 and a turbine portion 44. Compressorportion 42 includes a compressor inlet 46 that may be fluidicallyconnected to ambient and a compressor outlet 47 that may be fluidicallyconnected to an intake (not separately labeled) of diesel engine 26.Turbine portion 44 includes a turbine inlet 49 fluidically connected toexhaust system 30 and a turbine outlet 50 that may be fluidicallyconnected to aftertreatment system 34. Turbine outlet 50 delivers atleast a portion of exhaust gases passing through turbocharger 40 toaftertreatment system 34.

In accordance with an aspect of an exemplary embodiment, aftertreatmentsystem 34 includes a diesel cold start catalyst member 60 and a leanNO_(x) trap (LNT) member 64 arranged in a common housing 66. Whilearranged in a common housing, it is to be understood that diesel coldstart catalyst member 60 and LNT member 64 may exist in the commonhousing as separate components or bricks. Further, it is to beunderstood that diesel cold start catalyst member 60 and LNT member 64may each include a unique substrate with specific zone-coating thatprovides a separation between bricks. LNT member 64 is arrangeddownstream of diesel cold start catalyst member 60 as will becomeevident herein. Exhaust gases enter into, and raise an internaltemperature of, LNT member 64 after being processed by diesel cold startcatalyst member 60. Common housing 66 includes an inlet 69 fluidicallyconnected to turbine outlet 50 and an outlet 71 that is fluidicallyconnected to a transfer tube 74. Diesel cold start catalyst member 60operates to reduce NOx emissions in exhaust gases that are attemperatures below about 200° C. and LNT member 64 operates to reduceNOx emissions that may be present in exhaust gases that are at atemperature in excess of about 200° C. In this manner, diesel cold startcatalyst member 60 and LNT member 64 operate in tandem to reduce NOxemissions that may be present in exhaust gases from initial start up tonormal operating conditions.

More specifically, at initial startup, the temperature of exhaust gasespassing from internal combustion engine system 24 is typically below200° C. Diesel cold start catalyst member 60 may include a catalystand/or zeolite trap (not separately labeled) configured to reduce NOxemissions in exhaust gases at start up temperature. Exhaust gastemperatures starts to climb with continued operation of internalcombustion engine system 24 and LNT member 64 is heated. As exhaust gastemperatures approach operating temperatures of about 200° C. or higher,diesel cold start catalyst member 60 begins to lose NOx emissionreduction efficacy. However, LNT member 64, being heated by the exhaustgases passing from diesel cold start catalyst member 60, has reached aneffective operating temperature. As such, as the efficacy of diesel coldstart catalyst member 60 drops, LNT member 64 takes over to continue toreduce NOx emissions.

In further accordance with an exemplary aspect, a transfer tube 74includes an inlet portion 77 fluidically connected to outlet 71 and anoutlet portion 79 fluidically connected to a selective catalystreduction (SCR) system 84. SCR system 84 may also take the form of anSCRF system which includes a diesel particulate filter system. SCRsystem 84 processes the exhaust gases passing from LNT member 64 tofurther reduce emissions. SCR system 84 includes an inlet section 86fluidically connected to outlet portion 79 of transfer tube 74 and anoutlet section 88 that may be connected to a rear oxidation catalyst(ROC) 91 through an exhaust conduit 94. ROC 91 is fluidically connectedto exhaust outlet pipe 36 and operates to oxidize gases such as CO, HC,and NH3 that may pass from SCR system 84.

In still further accordance with an aspect of an exemplary embodiment, adiesel exhaust fluid (DEF) injection system 114 may be arrangeddownstream of LNT member 64 and upstream of SCR system 84. DEF injectionsystem 114 may be selectively controlled to introduce an amount ofdiesel exhaust fluid into the exhaust gases passing through, forexample, transfer tube 74. In accordance with an aspect of an exemplaryembodiment, DEF injection system 114 includes a urea injector. It is tobe understood that DEF injection system 114 may be configured tointroduce a wide range of diesel exhaust fluids into the exhaust gasespassing into transfer tube 74. The introduction of diesel exhaust fluidmay be controlled based on inputs from various sensors associated withaftertreatment system 34 to still further reduce emissions, particularlyNO_(x).

In still further accordance with an exemplary aspect, aftertreatmentsystem 34 may include a first O₂/NOx sensor 124 arranged in inlet 69 ofcommon housing 66 and a second O₂/NO_(x) sensor 125 arranged at outlet71 of common housing 66. Additionally, a first exhaust gas temperature(EGT) sensor 130 is arranged in inlet 69 and a second EGT sensor 131 isarranged at outlet 71. Also, a first differential pressure sensor (DPS)134 is arranged at inlet section 86 of SCR system 84 and a second DPS135 is arranged at outlet section 88 of SCR system 84. Each of the abovesensors may be connected to a controller (not shown) which may beemployed to control aspects of turbocharger 40, such as waste gateposition, DEF injection system 114 and the like.

It is to be understood that exemplary embodiments describe a system forreducing NOx emissions produced by an internal combustion engine duringboth a cold start period and normal operating conditions. The dieselcold start catalyst (diesel cold start catalyst) member of the presentinvention is positioned so as to both process exhaust gases during acold start or gases at temperatures below about 200° C. as well asprovide a pre-heat function for a lean NO_(x) trap positioneddownstream. In this manner, the exemplary embodiment eliminates the needfor electric pre-heaters that must be operated to pre-heat the LNTmember. Further, the particular arrangement of components provides abroader range of emission reduction that spans cold start, e.g., belowabout 200° C., and normal operation, e.g., exhaust temperatures aboveabout 200° C., in order to meet new emission regulations.

The term “about” is intended to include the degree of error associatedwith measurement of the particular quantity based upon the equipmentavailable at the time of filing the application. For example, “about”can include a range of +8% or 5%, or 2% of a given value. Further, theterm “about” should be understood to represent a general indication oftemperature values as particular temperature values may be dependentupon various system constraints, materials employed and the like.

While the above disclosure has been described with reference toexemplary embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from its scope. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the disclosure without departing from the essentialscope thereof. Therefore, it is intended that the invention not belimited to the particular embodiments disclosed, but will include allembodiments falling within the scope of the application.

What is claimed is:
 1. An aftertreatment system for an internalcombustion engine comprising: a diesel cold start catalyst member; alean NOx trap (LNT) member arranged directly adjacent to and downstreamof the diesel cold start catalyst; and a selective catalyst reduction(SCR) member arranged downstream of the LNT, wherein the diesel coldstart catalyst is operable to reduce NOx emissions at operatingtemperatures below 200° C. and the LNT and SCR system are operable toreduce NOx emissions at operating temperatures above 200° C.
 2. Theaftertreatment system according to claim 1, further comprising: a dieselexhaust fluid (DEF) injection system operable to introduce a dieselexhaust fluid into exhaust gases produced by the internal combustionengine.
 3. The aftertreatment system according to claim 2, wherein theDEF injection system is arranged downstream of the LNT and upstream ofthe SCR.
 4. The aftertreatment system according to claim 2, furthercomprising: a transfer tube fluidically connecting the diesel cold startcatalyst and LNT with the SCR.
 5. The aftertreatment system according toclaim 3, wherein the DEF injection system is fluidically connected tothe transfer tube.
 6. The aftertreatment system according to claim 2,wherein the DEF injection system comprises a urea injector.
 7. Theaftertreatment system according to claim 1, further comprising: at leastone of an O2/NOx sensor and an exhaust gas temperature (EGT) sensorarranged upstream of the diesel cold start catalyst, and at least one ofan O2/NOx sensor and an EGT sensor arranged downstream of the LNT. 8.The aftertreatment system according to claim 1, further comprising: afirst differential pressure sensor (DPS) arranged upstream of the SCRand a second DPS arranged downstream of the SCR.
 9. The aftertreatmentsystem according to claim 1, wherein the diesel cold start catalyst andLNT are arranged in a common housing.
 10. The after treatment systemaccording to claim 1, further comprising: a rear oxidation catalyst(ROC) arranged downstream of the SCR.
 11. A motor vehicle comprising: aninternal combustion engine including an exhaust system; and anaftertreatment system fluidically connected to the exhaust system, theaftertreatment system comprising: a diesel cold start catalyst member; alean NOx trap (LNT) member arranged directly adjacent to and downstreamof the diesel cold start catalyst; and a selective catalyst reduction(SCR) member arranged downstream of the LNT, wherein the diesel coldstart catalyst is operable to reduce NOx emissions at operatingtemperatures below 200° C. and the LNT and SCR system are operable toreduce NOx emissions at operating temperatures above 200° C.
 12. Themotor vehicle according to claim 11, further comprising: a dieselexhaust fluid (DEF) injection system operable to introduce a dieselexhaust fluid into exhaust gases produced by the internal combustionengine.
 13. The motor vehicle according to claim 12, wherein the DEFinjection system is arranged downstream of the LNT and upstream of theSCR.
 14. The motor vehicle according to claim 12, further comprising: atransfer tube fluidically connecting the diesel cold start catalyst andLNT with the SCR.
 15. The motor vehicle according to claim 14, whereinthe DEF injection system is fluidically connected to the transfer tube.16. The motor vehicle according to claim 10, wherein the DEF injectionsystem comprises a urea injector.
 17. The motor vehicle according toclaim 10, further comprising: a diesel exhaust fluid (DEF) injectionsystem arranged downstream of the LNT.
 18. The motor vehicle accordingto claim 10, further comprising: at least one of an O2/NOx sensor and anexhaust gas temperature (EGT) sensor arranged upstream of the dieselcold start catalyst, and at least one of an O2/NOx sensor and an EGTsensor arranged downstream of the LNT.
 19. The motor vehicle accordingto claim 10, further comprising: a first differential pressure sensor(DPS) arranged upstream of the SCR and a second DPS arranged downstreamof the SCR.
 20. The motor vehicle according to claim 10, wherein thediesel cold start catalyst and LNT are arranged in a common housing.